Exploration for oil by soil analysis



Nov. 29, 1955 D Q BOND EXPLORATION FOR 011. BY SOIL ANALYSIS 2Sheets-Sheet 1 Filed Dec. 29, 1950 FIGJ f f f INVENTOR.

DONALD C. BOND ATTORNEY Nov. 29, 1955 D, c, O 2,725,281

EXPLORATION FOR OIL BY SOIL ANALYSIS Filed Dec. 29, 1950 2 Sheets-Sheet2 24 22 25 OOOOOOO({OOOOOOOOJ1//2I INVENTOR.

ATTORNEY United States Patent O EXPLORATION non on. BY son. ANALYSISDonald C. Bond, Crystal Lake, 111., assignor to The Pure Oil Company,Chicago, $1., a corporation of Ohio Application December 29, 195i),aerial No. 203,246

8 Claims. (Cl. 23-230) The present invention relates to a method ofgeochemical prospecting for underground petroleum deposits, and moreparticularly, to a method and apparatus for measuring and interpretinggeochemical results.

It has long been known that through the geological ages there has beenan effusion of hydrocarbons through the relatively imperviousunderground rock formations due to the pressures and concentrationgradients which exist in petroleum accumulations. Mining geologists andpetroleum geologists have studied both the geology and geochemistry ofearth formations in their efforts to discover methods of prospectingwhich give a direct indication of the actual presence or absence ofpetroleum rather than the indirect geophysical methods. There hasdeveloped the art of microscopic geochemical prospecting which has ledto the discovery of many geochemical anomalies within earth structures.One of these discoveries has been called the halo theory which is ageochemical manifestation of the presence of a petroleum accumulationwhich may result from a nearsurface or near-deposit analysis of theformation for the presence of hydrocarbons that have leaked from theformation bearing petroleum. More specifically, surrounding eachpetroleum accumulation or area of production, there will exist a zone ofgeochemical influence produced by the slow effusion of hydrocarbons fromthe area of production upwardly to the earths surface, and therefore,surrounding the area of production will be a zone of higherconcentration of hydrocarbons. The near-surface geochemical analysiswill, of course, be influenced by any existing surface and subsurfaceanomalies especially effecting deep-seated deposits. The results of manyexperiments conducted at the surface around known producing areas hasdefinitely established the efficacy of the halo theory and the value ofits use as a means of geochemical prospecting. For a more completediscussion of the halo theory, reference is made to GeophysicalProspecting for Oil, by Nettleton, published 1940 by McGraw-HillCompany.

This chemical method of prospecting, to which the present inventionrelates, is based on the idea that the lighter hydrocarbons associatedwith petroleum would penetrate the overlying earth formations and spreadupward therethrough. Sufiicient quantities of these hydrocarbon gasesshould be present in the surface soil overlying petroleum accumulationsto detect by existing analytical methods. The concentration ofhydrocarbons found in the surface soil is said to be proportional to thequantity of petroleum from which they have diffused. Such hydrocarbonsas ethane and propane are known only to emit from petroleum deposits andnot to come from the decomposition of vegetation.

It has been theorized that as the escaping hydrocarbons migrate upwardlyto zones of lower pressure, they take on the gaseous phase and thiscontinuous increase in volume causes the evaporation of connate watersand the concentration of minerals therein. There results a replacementof this evaporated ground water by diffusion which the ascendinghydrocarbons would assume and there results a direct correlation betweentypical hydrocarbon halos, annular seismic anomalies, and gravitychanges with even deep-seated accumulations.

The methods of hydrocarbon analysis usedin detecting small quantitieswithin soil samples vary widely. The most successful method is based onthe difference in vapor pressure characteristics of the different gasesfound in the soil samples by cooling the mixture to liquid-airtemperatures and then applying suflicient heat to slowly vaporize theconstituents which are given off at different temperatures. The relativequantities of each hydrocarbon gas so separated are determined bychemical analysis. Minute quantities of each constituent can beaccurately detected by the presently developed chemical analysismethods. Other recently developed methods which are proving successfulare based on occluded gases pumped off from a soil sample or.extractedtherefrom by solvents. a v

The procedure involved in discovering the presence of these anomaliesand the halo effect is to'collect .soil samples at spaced andpro-determined points over an area of the earths surface to'be exploredat depths from a few inches to several feet in the ground. The points ofsampling and the depths are accurately plotted ona contour map of thearea and are usually spaced at in-' tervals of about mile. The samplessotaken are then carefully analyzed for their hydrocarbon;content andthe results are plotted on the map at the corresponding sampling points.Then those points which. represent nearly the same concentrations ofhydrocarbons are connected by a line and the halo established. Eachhydrocarbon constituent analyzed for may be plotted on a separate mapand final interpretation .is made either by comparison of the maps or byconnecting the points of equal hydrocarbon content. Experience hasindicated that there is a tendency for those hydrocarbons associatedwith petroleum to be more concentrated around the periphery of theoil-bearing formation from which they diffuse. When this is brought outby plotting and connecting points on a map, the area of said concentration is known as the halo surrounding a possible producing formation.This halo is closely related to the subterranean petroleum reservoir andthe accuracy with which it is established depends on the accuracyoftheinterpretation of the hydrocarbon analyses by the .-in-- terpreter.

The present invention is directed to a method and appa effect ofhydrocarbon effusion from an unknown petrole urn reservoir.

The apparatus and method described herein is designed to eliminate thesubjective element in geochemical interpretation and to place before theobserver an accurate indication of the relationship between thevariation of hydrocarbon content in the soil andthe strategraphic con.-

. tour of the area under geological survey. 1

The invention is best explained by reference to the drawings. Figure 1is an isometric view of a cartograph and screen for use in practicingtheinvention. Figure 2 is an end elevational view of one possible specificform of apparatus of the type generally shown in Figure 1. Figure 3 isan isometric view of another embodiment of the invention illustratingthe use of magnets to impart their magnetic field'npon magnetic metalparticles which orient themselves and accumulate in concentrationsproportional to and in accordance with the field intensity. Figure 4- isa diagram of one possible electrical control circuit for the apparatus.

In Figure 1, the cartograph is any map, chart or other representationof' an area to be investigated. Cartograph 1 has distinguishing lines 2for the purpose of identifying the area and ultimately disclosing thelocation of the halo etfect thereon. Projecting through the cartographare indicators 3 which are positionable in any chosen pattern overthesurface of the cartograph 1. The indicators 3 comprise means fortransmitting detectable forms of energy such as light or magnetism andare adapted to emit such energyin varyingintensity depending on theamount of regular input which is adjustable so as to be proportional tothe values of the hydrocarbon analyses at the corresponding point on thecartograph. Each indicator 3 may be adjustable in its position on thecartograph so that it may beplaced ina position conforming to the pointat which a soil analysis was made. The distance between points of soilanalysis may be varied depending upon the size of the area beingexplored and the geological history of the area. Generally, the distancebetween points of soil analysis will be about ,4 mile during the actualsample-taking. The cartograph of the area is scaled to a workable sizeand may be as small as 10 feet by 10 feet or as large as is convenientfor handling.

Transposed upon, and immediately adjacent to cartograph 1 and indicators3 is screen 4 having the same dimensions as cartograph 1. Screen 4 ismade of material which is resistant to the form of energy given olf byindicia 3. Also screen 4 should be of uniform texture and be uniformlytransparent to or sensitive to the energy produced by indicators 3.Where the form of energy to be recorded is light the screen 4 may becomposed of translucent paper, ground glass, parchment, oiled or waxedpaper. Screen 4 may be ordinary paper, as tracing paper, where the formof energy to be recorded or measured is magnetism.

With screen 4 in position adjacent to cartograph 1 and with eachindicator 3 transmitting energy of an intensity corresponding to thehydrocarbon content of the soil at the corresponding point on thecartograph 1, there will be produced upon screen 4 a summation of theenergy intensities. At those points upon the cartograph where thehydrocarbon analysis is higherthan other points due to the infusion ofhydrocarbon gases through the earth formations from a subterraneandeposit, there will be produced an area or circle of greater response 5which may be visible to the naked eye or which can be photographed,traced or otherwise recorded. The over-all amount of energy passingthrough all of the indicators 3 may be adjusted so that the energytransmitted will be just sufiicient for those of highest intensity to berecorded through the screen 4. The indicators of lowest energy contentwill then be practically indetectable through the screen 4. This willsharpen the halo image. The last described technique can be accomplishedby variable control of the overall'energy intensity of the indicators 3after the circuit to each has been supplied with an amount of energyproportional to the hydrocarbon content of the soil at the point ofsampling. Where electrical energy is used to activate the indicators,one possible circuit for controlling the energy intensities may berepresented by Figure 4, wherein 41-is a variable transformer, 110 v. A.0, R1, R2, R3, R4, R5, and Rs are variable resistors and B1, B2, B3, B4,Bs,and B6" are the indicators.

After adjustment of =the-over-all-intensity so that the halo has beensharpened, the observer may place a thin sheet of tracing paper over thearea which discloses the halo and then trace on the paper the locationof the best halo or halos. Thereafter, the assemblage of indiciators maybe rotated or moved laterally without knowledge of the observer andrepeated tracings will be taken. These various tracings may then becompared one upon the other to obtain the best halo and its location onthe cartograph may be accurately placed by comparison with thedistinguishing lines 2. The interpretation of one observer may bechecked by having several observers make similar interpretations. Wherelight is the type of energy to be recorded the entire operation isconducted in a room which is totally dark and observations are madeafter allowing from 15 to 30 minutes to transpire for the eyes to becomeaccustomed to darkness. Under these conditions, any existing backgroundillumination which has not been eliminated by the over-all voltageinfluencing the indicators will disappear.

Figure 2 is an end view of one possible form of apparatus comprising atable 20 upon which is placed contour map 21 representing one form ofcartograph. Through contour map 21, project one form of indicator, thelight bulbs 22. Clamps 23 are provided along the edge of the table 20tohold translucent screen 24 rigidly and in juxtaposition with the lightbulbs 22 and contour map 21. The distance between the light bulbs 22 andthe translucent screen 24 may be adjusted so that there is a minimum ofdistortion due to the heat elfect of the light bulbs. Ventilation may beprovided between the translucent screen 24 and the light bulbs 22 tosubstantially eliminate this distortion. Clamps 23 with aninterimposed-sheet of glass (not shown) will'hold translucent screen 24sufficiently rigid to enable the tracing of the best halos.

The electric light bulbs 22 are anyordinary type of electric light bulbwhich will give an illumination of constant intensity for a given amountof electricity. Preferably frosted bulbs are used which require only afraction of a watt during maximum intensity. Bulbs may be used havinghigher voltage, as for example, 1 to 10 watts. The size of the bulbswith respect to the size of the map is adjusted so that the illuminationtransmitted therefrom is controllable to produce the halo effectdesired. The current for controlling the intensity ofilluminating lightbulbs 22 may again be represented by Figure 4 wherein 41 is a variabletransformer, volt A. C., R1, R2, R3, R4, R5, and Rs are the variableresistors and B1, B2, B3, B4, B5, and B6 are the electric light bulbs.

Figure 3 shows a table 30 upon which is placed contour map 31 havingcontour lines 32 similar to distinguishing lines 2 shown in Figure 1.Small electromagnets 33, which serve as indicators, are placed at pointsof hydrocarbon soil analysis directly underneath the contour map. Eachelectromagnet is connected through control cable 34 to individualrheostats within control panel35.

The electrical circuit within control panel 35 is also represented byFigure 4 wherein 41 is a variable trans former, 110 volt A. 0., R1, R2,R3, R4, R5 and Rs are the variable resistors or rheostats mentioned andB1, B2, B3, B4, B5, and B6 may be the electromagnets controlled.thereby.

The rheostats-are individually adjusted to an arbitrary valueproportional to the concentration of hydrocarbon gaszfound at that.point in the geochemical survey, thereby establishing within eachelectromagnet 33- of table 36 a magnetic field of correspondingintensity. Control panel 35 is fitted with voltmeter 36, ammeter 37, andvoltage control switch 38, for purposes of setting up the minimumover-all field intensity necessary to bring out thehaloeffect.

Dnplicatecontour map 39 is shown in raised position above contour map 31for purposes of illustration. In

actual operation, the duplicate contour map 39 will be in juxtapositionwith contour map 31 so that the multitude of magnetic fields set up bythese small electromagnets 33 will penetrate duplicate contour map 39.

After each electromagnetic indicator 33 is receiving an amount ofcurrent proportional to the soil analysis of the point on the contourmap 31, which it represents, by proper adjustment of the variousrheostats on control panel 36,- the operator will adjust voltage controlswitch 38 so that the minimum field intensity will penetrate through theduplicate contour map 39/ This minimum field of influence is thendetected by sprinkling metal or metal alloy particles 40 thereon, whichare attracted by the magnetic field. Upon vibration or tapping ofcontour map 39, metal particles 40 will orient themselves in accordancewith the magnetic field encountered. At individual points upon thesurface of contour map 39, the metal particles will attain aconcentration which is proportional to the magnetic field intensity atthat point. Any changes in concentration due to changes in'magneticfield intensity will be immediately visible to the naked eye or may bephotographed. Vibration or tapping is used to hasten the orientation ofthe iron filings. For this purpose, an electric vibrator may be used orthe orientation may be hastened by intermittent application of currentthrough control panel 35. If the soil analysis has been made over anarea on the earths surface which is above a petroleum reservoir, whichis etlusing hydrocarbons from under a cap rock or similar geologicalstructure, there will be produced a halo effect.

One advantage, which is apparent from the embodiment shown in Figure 3,is that the current may be stopped momentarily and the metal particlesevenly distributed over contour map 39. Then, upon reapplication ofcurrent through the electromagnets 33, followed by vibration of contourmap 39, there will result a rapid reorientation of the metal particles.In this manner, repeated determinations can easily and rapidly be madefrom which the best halo may be outlined.

From the above discussions of the invention, it is apparent that whereelectrical illumination or magnetic fields are utilized to establish thehalo effect, the accuracy of the determination is dependent upon aphysical phenomena rather than the subjective element of an observertrying to plot or join those points of soil analysis having the same orsimilar hydrocarbon concentrations as is used in the prior art. Theaccuracy of the present method is, of course, dependent upon theaccuracy of the soil analysis technique and the sensitiveness of themeans used to impart energy into the indicators, namely, theelectromagnets or the electric light bulbs. However, the sensitivity ofpresently-known energy transmitting instruments as for exampleelectrical instruments, magnets and light bulbs is such that thesubjective element is removed by the present method.

It is apparent that changes in the procedure and apparatus from thatmentioned above can be adopted without departing materially from thescope of the present invention. The metal particles used to detect themagnetic field of influence may be any material which has a magneticsusceptibility comparable to that of iron or is at least paramagnetic incharacter. Examples of suitable materials are iron filings, iron-nickelalloys, as alloys of iron and nickel having between 45% and 80% nickel,or nickel and cobalt alloys.

Although specific embodiments of the present invention have beendescribed, they are to be taken as only illustrative and the onlylimitations which exist are those appearing in the following claims.

What is claimed is:

1. A method for prospecting for subterranean petroleum depositscomprising the steps of collecting a plurality of soil samples at spacedpoints over an area of the earths surface to be explored, analyzing saidsoil samples for their hydrocarbon content, releasing detectable formsof energy at a plurality of unshielded points on a cartograph of saidarea corresponding to said points of sampling, adjusting the magnitudeof said energy at each point of release to correspond and beproportional to the value of said hydrocarbon content of thecorresponding point of sampling, transmitting the accumulative summationof said energy upon means for detecting the relative density thereof,reducing the total energy input to said unshielded points on saidcartograph until the points of highest intensity on said detecting meansare substantially extinct, thereupon gradually increasing the totalenergy input to said points to produce an area of highest detectableaccumulative energy emission and recording such area to thereby locatein relation to said cartograph the halo efiect produced by saidhydrocarbons from said petroleum deposits.

2. The method for prospecting for subterranean petroleum depositscomprising the steps of collecting a plurality of oil samplesat spacedpoints over an area of the earths surface to be explored, analyzing saidsoil samples for their hydrocarbon content, releasing illumination at aplurality of unshielded points on a cartograph of said areacorresponding to said points of sampling, adjusting the magnitude ofillumination at each point of release to correspond and be proportionalto the value of said hydrocarbon content of the corresponding point ofsampling, transmitting the accumulative summation of said illuminationupon meansj for detecting the relative intensity thereof, reducing thetotal amount of illumination from said unshielded points in equivalentvalue until the points of highest intensity on said detecting means aresubstantially extinct, thereupon gradually increasing the totalillumination input to said points to produce an area of highestdetectable accumulative illumination and recording such area to therebylocate in relation to said cartograph the halo efiect produced by saidhydrocarbons from said petroleum deposits.

3. The method in accordance with claim 2 in which said recording step iscarried out by photographing the highest detectable accumulativeillumination.

4. The method for prospecting for subterranean petroleum depositscomprising the steps of collecting a plurality of oil samples at spacedpoints over an area of the earths surface to be explored, analyzing saidsoil samples for their hydrocarbon content, establishing a plurality ofunshielded variable electromagnetic fields at points on a cartograph ofsaid area corresponding to said points of sampling, adjusting themagnitude of said electromagnetic fields at each point to correspond andbe proportional to the value of said hydrocarbon content of thecorresponding point of sampling, suspending discrete paramagneticparticles in free-moving relationship within said magnetic fields soproduced, agitating said paramagnetic particles while lowering thestrength of said magnetic fields in proportionate amounts until thestrongest magnetic fields corresponding to the highest hydrocarboncontent barely orient and attract said paramagnetic particles,increasing the strength of said magnetic fields proportionately untilthe greatest detectable accumulative group of oriented paramagneticparticles is established, and recording the location of said detectablegroup to thereby locate in relation to said cartograph the halo elfectproduced by said hydrocarbons from said petroleum deposits.

5. An apparatus for prospecting for subterranean petroleum depositscomprising in combination a cartograph of the area explored, a pluralityof spaced individual unshielded indicators movably mounted on one sideof said cartograph, means for fixing said indicators at places on thecartograph which correspond to points of surface oil analyses forhydrocarbons over said area, a source of energy connected to each ofsaid indicators, means for adjusting the amount of energy imparted toeach of said indicators to values which are proportional to therespective soil analysis values for the corresponding sampling point ofthe area, means for varying simultaneously the total amount of energyimparted to all of said indicators so that the accumulated energyemission from all indicators maybe brought-to extinction, and-means fordetecting andrecordi-ng the relativeintensity of the area of greatestdetectable. accumulative energyemission from those indicators receivingthe most'energy, to thereby locate inv relation tosaidcartographthe-halo effect .produced by said hydrocarbonsfrom saidpetroleum deosits.

p 6. An apparatus for prospecting for subterranean petroleum depositscomprising incombination a plane .surface cartograph of the areaexplored, a plurality of spaced individual unshielded light-sourcesmovably'mounted on one side of the plane. surface of .said cartograph,means for fixing said light sources at places on the cartograph whichcorrespond to points of surface soilanalysis-for hydrocarbons over saidarea, a variable transformer connected to a source of electricalcurrent,said light sources being connected in parallel to said variabletransformer so that the total amount of electrical current supplied tosaid light sources maybe varied simultaneously to reduce the accumulatedlight emissiontherefrom to:eiitinction,.a variable resistor connected inseries with eachlight source to adjust the amount of current supplied toeachlight source to values which correspond to the respective values ofthe soil analysis at corresponding points, and means for detecting andrecording the relative intensity :of the area of greatest detectableaccumulative light emission from those light sources receiving the mostcurrent to thereby locate in relation to said car-tograph the haloeffect produced by said hydrocarbons from said petroleumdeposits.

7. An apparatus for prospecting for subterranean petrole'u'rn depositscomprising in combination a plane surface cartograph of the areaeXplored,- a plurality of spaced individual unshielded electromagnetsmovably mounted on one side of the plane surface of said cartograph,means for fixin g said elec-tromagnets at places on the cartograph whichcorrespond to points of surface soil analysis .for hydrocarbons 'oversaid area, a' variable transformer connected to a source ofv electricalcurrent, said electromagne-ts being connected in parallel to saidvariable transformer so that the total amount ofelectrical currentsupplied to said electromagnets may be varied simultaneously toreduce-the accumulative magnetic field therefrom to extinct-ion, avariable resistorconnected in series with each electromagnet to adjustthe magnitude of the magnet-ic field produced by each mag-net tocorrespond to the respective values of the soil analyses atcorresponding points, and means for detecting and recording the area ofgreatest detectable accumulative magnetism from said magnets to therebylocate in relation to said cartograph the halo effect produced by saidhydrocarbons from said petroleum deposits.

8. An apparatus in accordance withclaim 7 in which the means fordetecting andxrecording the greatest detectable accumulativemagnetismproduced by said magnets comprises a sheet of non-magnetic materialhaving a surface area substantially the same as that of said cartograph,said non-magnetic sheet being-held horizontally in juxtaposition withsaid cartograph and adapted to suspend discrete paramagnetic particleswithin the influence of the plurality of magnetic fields set up by saidelectromagne-ts, and means for agitating said non magnetic sheet.

References Cited in the file of this patent UNITED STATES PATENTS2,269,889 Blau Jan. 13;1'942 2,317,590 Compete Apr. 27,1943 2,367,592McDermott Jan. 16, 1945 2,417,043 prewar at al. Mar. 11, 1947 2,567,189Davis -t "Sept. 11, 1951

1. A METHOD FOR PROSPECTING FOR SUBTERRANEAN PETROLEUM DEPOSITCOMPRISING THE STEPS OF COLLECTING A PLURALITY OF SOIL SAMPLES AT SPACEDPOINTS OVER AN AREA OF THE EARTH''S SURFACE TO BE EXPLORED, ANALYZINGSAID SOIL SAMPLES FOR THEIR HYDROCARBON CONTENT, RELEASING DETECTABLEFORMS OF ENERGY AT A PLURALITY OF UNSHIELDED POINTS ON A CARTOGRAPH OFSAID AREA CORRESPONDING TO SAID POINTS OF SAMPLING, ADJUSTING THEMAGNITUDE OF SAID ENERGY AT EACH POINT OF RELEASE TO CORRESPOND AND BEPROPORTIONAL TO THE VALUE OF SAID HYDROCARBON CONTENT OF THECORRESPONDING POINT OF SAMPLING, TRANSMITTING THE ACCUMULATIVE SUMMA-